1. Field of the Invention
The present invention relates to a gear grinding tool having a helical tooth that meshes with a rotating gear to grind the gear. The present invention also concerns a method of using such a gear grinding tool.
2. Description of the Related Art
Generally, gear grinders include a tool shaft, which holds a gear grinding tool having a helical tooth and a workpiece shaft that holds a gear, which serves as a workpiece. During operation, the tool shaft and the workpiece shaft rotate in synchronism with each other in order to grind the tooth faces with the gear grinding tool.
Such tooth faces often are ground separately in two stages, i.e., a rough grinding stage and a finishing stage. The rough grinding stage and the finishing stage make use of a rough grinding tool and a finishing tool, respectively, to successively perform corresponding grinding processes on the tooth faces in order to grind the tooth faces to a desired finish level.
Japanese Laid-Open Patent Publication No. 2005-305645 discloses a gear grinding tool having a rough grinding region and a finishing region, which are arrayed along an axial direction of the gear grinding tool, and which overlap each other along the axial direction.
The gear grinding tool disclosed in Japanese Laid-Open Patent Publication No. 2005-305645 is capable by itself of successively performing a rough grinding process and a finishing process. However, the disclosed gear grinding tool is disadvantageous in that the service life of the finishing area thereof may end earlier than the service life of the rough grinding region. Thus, because the finishing region has a grinding surface that is finer than the rough grinding region and tends to become worn and rendered unusable sooner than the rough grinding region, the gear grinding tool could possibly fail to achieve a desired level of machining accuracy. Further, once the finishing area becomes worn out, the rough grinding region, which actually is still capable of being used, is rendered useless, with the result that the service life of the gear grinding tool as a whole is shortened.